The field of application of the invention is that of large capacity point-to-point digital radio transmission. This type of transmission uses travelling wave tube amplifiers or solid state amplifiers (e.g. an ASGA field effect transistor (FET)).
The modulation used for this type of transmission (16 QAM, 64 QAM) requires the transmission chain to have excellent linearity, and conventionally this is obtained by considerably overspecifying the amplifier.
For example, a solid state amplifier may be:
run at 6 dB to 7 dB below full power for 16 QAM; or PA1 run at 8 dB to 10 dB below full power for 64 QAM. PA1 with 16 QAM: power consumed=40 W, output power=5 W PA1 with 64 QAM: power consumed=90 W, output power=10 W.
Consequently power amplifier efficiency is particularly bad. For example:
The object of the invention is to mitigate these various drawbacks.